REFERENCE
The watch glossary
Every watch and horology term, in plain English — from automatic and chronograph to tourbillon and water resistance. Bookmark it, and never nod along to a term you don’t know again.
A
- Applied indices
- Hour markers that are separately made and attached to the dial (rather than printed), giving depth and a premium look.
- Automatic
- A mechanical watch that winds itself using a rotor that turns with the motion of your wrist — no battery required.
B
- Bezel
- The ring around the crystal. It can be fixed, or rotating (as on a dive watch, to time an interval).
- Bracelet
- A metal band made of links, as opposed to a leather, rubber or fabric strap.
C
- Caliber (calibre)
- The specific movement inside a watch, usually identified by a name or number (e.g. Seiko 6R35).
- Chronograph
- A watch with a built-in stopwatch, operated by pushers, with subdials to record elapsed time.
- Chronometer
- A watch whose movement has passed an independent precision test such as COSC — not the same as a chronograph.
- Complication
- Any function a watch performs beyond telling the time — date, chronograph, GMT, moonphase, and so on.
- COSC
- The Swiss Official Chronometer Testing Institute, which certifies movement accuracy to roughly −4/+6 seconds per day.
- Crown
- The knob on the case side used to set the time and date and, on mechanical watches, to wind the movement.
- Crystal
- The transparent cover over the dial — usually sapphire (very scratch-resistant), mineral glass, or acrylic.
D
- Deployant clasp
- A folding clasp that expands to slip over your hand, then folds shut — safer and easier than a pin buckle.
- Dial
- The face of the watch, carrying the hour markers, hands and any subdials or text.
- Diver / dive watch
- A water-resistant watch built for diving, typically 200m+ with a unidirectional bezel and strong lume (often ISO 6425 rated).
E
- Escapement
- The mechanism that releases the mainspring’s energy in tiny, regular beats — the heart of a mechanical watch’s timekeeping.
- Exhibition caseback
- A transparent (usually sapphire) caseback that lets you see the movement.
F
- Frequency
- How fast a movement beats, measured in vph (vibrations per hour) or Hz — higher frequency generally means a smoother sweep.
G
- GMT
- A complication that shows a second time zone via an extra 24-hour hand, ideal for travellers.
- Guilloché
- Fine, repeating engraved patterns on a dial, traditionally cut by hand on a rose engine.
H
- Hacking seconds
- A feature where pulling the crown stops the second hand, letting you set the time precisely.
- Helium escape valve
- A valve on saturation dive watches that lets built-up helium escape during decompression without damaging the watch.
- Homage
- A watch designed to evoke a famous model without copying its branding — distinct from a counterfeit.
- Horology
- The study and art of timekeeping and watchmaking.
I
- In-house movement
- A movement designed and built by the watch brand itself, rather than sourced from a third party like ETA or Sellita.
- ISO 6425
- The international standard a watch must meet to be marketed as a true “diver’s” watch.
J
- Jewels
- Synthetic rubies set at points of friction in a movement to reduce wear — a typical automatic has around 21–25.
L
- Lug width
- The distance between the lugs, which determines the strap size a watch takes (e.g. 20mm).
- Lug-to-lug
- The length of the case from the tip of one lug to the other — a key measure of how a watch will fit your wrist.
- Lume
- Luminous material on the hands and markers (e.g. Super-LumiNova) that glows in the dark after light exposure.
M
- Mainspring
- The coiled spring that stores energy in a mechanical watch; winding tightens it.
- Manual (hand-wound)
- A mechanical watch you wind by hand rather than through wrist motion.
- Manufacture
- A brand that makes its own movements in-house (from the French for a watchmaking house).
- Moonphase
- A complication that displays the current phase of the moon on the dial.
- Movement
- The engine of the watch — the mechanism that keeps time. Also called the caliber.
N
- NATO strap
- A single-piece woven nylon strap that passes under the caseback, so the watch stays on even if a spring bar fails.
P
- Power reserve
- How long a fully wound mechanical watch will run when not worn — commonly 38 to 80+ hours.
Q
- Quartz
- A battery-powered movement regulated by a vibrating quartz crystal — very accurate, with a ticking second hand.
R
- Rotor
- The weighted semicircle that swings with your wrist to wind an automatic movement.
S
- Sapphire crystal
- A synthetic sapphire crystal — extremely hard and scratch-resistant, the premium choice.
- Screw-down crown
- A crown that screws into the case to seal it, improving water resistance. Must be unscrewed to set the time.
- Subdial
- A smaller dial within the main dial, used for running seconds, chronograph counters or other functions.
T
- Tachymeter
- A bezel or dial scale that, with the chronograph, measures speed over a known distance.
- Tourbillon
- A rotating cage that houses the escapement to average out the effects of gravity — a showpiece of high watchmaking.
V
- Vph
- Vibrations per hour — the beat rate of a movement. 28,800 vph (4 Hz) is common.
W
- Water resistance
- A lab pressure rating (in metres or ATM) indicating how much water contact a watch can safely take. See our full guide.
Automatic vs quartz
The movements, with live dials.
Water resistance
What the ratings really mean.
Complications
Chronographs, GMTs & more.
Put the words to work
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